The 3GPP defines a high-speed uplink data communication which is referred to as “EUL (Enhanced Uplink)” or “HSUPA (High-Speed Uplink Packet Access).”
In EUL, a mobile station UE is configured to transmit a second protocol data unit (MAC-e PDU) containing one or more first protocol data units (MAC-d PDU) with a fixed data size to a radio base station NodeB via E-DPDCH (E-DCH Dedicated Physical Data Channel).
Specifically, in EUL, the radio base station NodeB is configured to determine a mobile station UE to be scheduled in each time slot (TTI: Transmission Time Interval) and transmit a scheduling grant information (AG: Absolute Grant, RG: Relative Grant) to the mobile station UE to be scheduled.
Also, the mobile station UE to be scheduled in each TTI is configured to transmit MAC-e PDU with TBS (Transport Block Size) according to an allowed value (SG: Scheduling Grant) determined by using the scheduling grant information (AG/RG) received via the E-DPDCH from the radio base station NodeB.
In addition, in EUL of the “Time and Rate” system, only one mobile station UE is treated as a mobile station UE to be scheduled in each scheduling assignment slot.
However, the aforementioned EUL of the “Time and Rate” system has a problem that it has not been determined yet what scheduling grant information (AG) the radio base station NodeB has to transmit at a time of switching between mobile stations UE to be scheduled.
Hence, the present invention has been made in view of the foregoing problem. Accordingly, an objective of the invention is to provide a mobile communication method and a radio base station which can notify proper scheduling grant information to a mobile station UE to be scheduled in the next scheduling assignment slot in EUL of “Time and Rate” system.